But that news is tempered by a pair of sobering realizations. First, we've been down this road before, and secondly, our "knowledge gaps" concerning North Korea's nuclear program are substantial. There is the very real possibility that Kim Jong-il may continue convert nuclear development (at home or abroad), while appearing to comply with the latest agreement.

Readers will recall that this isn't the first time that the Yongbyon reactor has gone off-line. Back in 1994, was idled as part of the "Agreed To" Framework between Pyongyang, Washington and Seoul. Under that agreement, the United States and South Korea agreed to provide fuel oil for heating and electricity, until the ROK government could build two light water reactors to replace the graphite-moderated plants in North Korea, which could produce weapons-grade plutonium. In return, Pyongyang agreed to close the Yongbyon facility, abandon two larger reactors (then under construction) and allow IAEA monitoring and inspections.

The presence of IAEA cameras and inspectors led John Kerry to brag about the "success" of the agreement during the 2004 Presidential campaign, and the corresponding "failure" of Bush Administration policies, which took a harder view toward North Korea. Mr. Kerry was referring to the collapse of the "Agreed To" framework in 2002, when the U.S. confronted Pyongyang about covert nuclear efforts, and North Korean diplomats confessed that their country had developed a small nuclear arsenal, in spite of the agreement.

Not surprisingly, Mr. Kerry--and other members of his party--got it wrong. Far from being an arms control success, the Agreed To Framework simply drove the North Korean program underground, where it continued unfettered. Critics of the Bush Administration have suggested that much of Pyongyang's nuclear development came after framework finally collapsed in 2002, but that belies an obvious fact. Without a convert program, which continued throughout the 1990s, it would have been difficult, if not impossible for Kim Jong-il's regime to announce that it had nuclear weapons in 2002, and follow that with a partially-successful test less than four years later.

Which brings us back to our original question: are we heading down the same path again? Pyongyang announced the shutdown of Yongbyon as a South Korean tanker arrived, bringing badly needed fuel oil for the DPRK. Under the Agreed To Framework, the U.S. and ROK provided up to 500,000 tons of oil a year; the Six-Party talks promised 50,000 tons for idling the Yongbyon plant, and another 950,000 tons of oil once the reactor has been fully disabled. Delivery of energy assistance is a major objective for Pyongyang.

So too, is the lessening of U.S.-led economic sanctions, which have been aimed (in part) at North Korea's ruling elites. Shutdown of the Yongbyon reactor was delayed, in part, by a dispute over $25 million in frozen North Korean assets in a Macau bank. The accounts apparently belonged to senior North Korean officials, or were used to purchase premium goods for members of the country's political and military leadership. While $25 million may sound like chump change by international banking standards, it was enough to stall implementation of the new agreement. With the release of that money--and the easing of other sanctions--North Korean achieved a second major goal.

So what is the United States--and its partners--getting in return? The shut-down of Yongbyon is a good first step, and the presence of IAEA inspectors at that site will provide a measure of reassurance. But the really hard work lies ahead, in getting North Korea to declare all of its nuclear programs and disable all of its nuclear facilities, as required under the new agreement.

And that's where things get a bit dicey. As we learned in North Korea in the late 1990s--and we may be learning again in Iran--it's relatively easy to conceal covert nuclear work. Even critical functions (such as uranium enrichment) can be hidden in underground facilities, or in non-descript buildings without any "overt" signature. Despite this latest agreement--and the return of IAEA inspectors to North Korea--it would be possible for Pyongyang to continue a covert program, with little fear of detection. The intelligence community has long admitted that its coverage of the DPRK nuclear program is far from complete, hindering verification and implementation of any agreement.

That's one reason that Senator Kerry's famous "camera comment" was so completely vacuous. The monitoring system at Yongbyon in the 1990s showed no activity because that's what the North Koreans wanted us to see. Meanwhile, the real work of advancing Pyongyang's nuclear ambitions was going on at other facilities, oblivious to the IAEA--or western intelligence. As the latest agreement enters its implementation phase, we can only wonder if Kim Jong-il is playing another nuclear shell game.

We should also worry about the "other" reasons Pyongyang might have for supporting the new accord. Perhaps North Korea believes its nuclear stockpile is sufficient for current purposes, and is willing to play along for a while, in exchange for sanctions relief, security guarantees and that vitally important energy assistance. Or, more ominously, the DPRK may have moved key portions of its nuclear program overseas, providing technical assistance for nations like Iran, and using the revenue earned to improve its own technology and designs.

Dealing with North Korea requires modification of Ronald Reagan's famous maxim of "Trust, But Verify." While the Bush Administration is committed to diplomacy in resolving issues on the Korean Peninsula, past agreements with Pyongyang provide little foudation for trust. And verification of full compliance will prove difficult, if not impossible.